Arrangement for controlling marine warning lights as a function of fog density

ABSTRACT

An electronic arrangement for automatically varying the characteristics of warning lights, at sea, independent of the prevailing fog. A platform or floating dock located on the surface of the water supports a warning light which is transmitted through Fresnel lenses. A receiver also located on the floating dock receives a portion of the signal reflected by the surrounding air particles. Under heavy fog conditions greater penetration of the warning light is accomplished by increasing the time duration of the flashing signal, rather than its amplitude. Automatic switching to a greater signal duration is realized with the receiver which receives a larger signal from the backscattered light during heavy fog conditions. When the received signal exceeds a predetermined threshold value, a relay is actuated and switches auxiliary circuit components for increasing the time interval of the transmitted signal.

United States Patent [72] Inventor Frank Fruengel 400, Sulldorfer Landstrasse, 2 Hamburg 56 Rissen, Germany [21] App]. No. 751,136 [22] Filed Aug. 8, 1968 [45] Patented Apr. 27, I971 [54] ARRANGEMENT FOR CONTROLLING MARINE WARNING LIGHTS AS A FUNCTION OF FOG DENSITY 6 Claims, 2 Drawing Figs.

[52] US. Cl. 340/236 [51] Int. Cl G08h 21/00 [50] Field of Search 340/236, 25, 377; 250/218, 205; 356/151 [56] References Cited UNITED STATES PATENTS 3,350,604 10/1967 Erickson 250/205 3,416,032 12/1968 Jahns et a1. 250/205 3,317,730 5/1967 Hilsum Primary Examiner-Robert L. Griffin Assistant Examiner-Barry Leibowitz Attorney-Michael S. Striker ABSTRACT: An electronic arrangement for automatically varying the characteristics of warning lights, at sea, independent of the prevailing fog. A platform or floating dock located on the surface of the water supports a warning light which is transmitted through Fresnel lenses. A receiver also located on the floating dock receives a portion of the signal reflected by the surrounding air particles. Under heavy fog conditions greater penetration of the warning light is accomplished by increasing the time duration of the flashing signal, rather than its amplitude. Automatic switching to a greater signal duration is realized with the receiver which receives a larger signal from the backscattered light during heavy fog conditions. When the received signal exceeds a predetermined threshold value, a relay is actuated and switches auxiliary circuit components for increasing the time interval of the transmitted signal.

FIG. 2 i

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ml (GP/f Il -kh- ATTORNEY ARRANGEMENT FOR CONTROLLING MARINE WARNING LIGHTS AS A FUNCTION OF FOG DENSITY BACKGROUND OF THE INVENTION Marine warning lights are in normal use wherever obstructions exist in the sea which would be damaging to ships and mariners. Such obstructions may be in the form of the natural underwater terrain, sunken vessels, or oil exploration equipment. To prevent mariners from entering such a hazardous area, warning lights are generally mounted upon buoys, towers, or floating docks. The warning light is usually a flashing light so that it may be readily observed. The flashing warning light is designed so that it is clearly visible to the human eye of a mariner, for example, at predetermined distance from source of the light. This arrangement permits the mariner to change his navigational course, if necessary,

and thus avoid the obstruction.

When fog conditions set in, the warning light would be visible only at a reduced distance from the light source. In order to prevent hazardous conditions for mariners, therefore, it is essential to increase the penetration of the light during such fog conditions so that it may be readily seen at a sufficiently long distance from the source. Such increased penetration of the warning light may be accomplished through two methods:

In one common arrangement the amplitude of the light intensity is increased so as to have greater penetration capability. Another method makes use of the fact that the visibility of the light by the human eye is a function of the time integral of the light intensity. Thus, a high amplitude narrow pulse may be as readily detected by the human eye as a light pulse of smaller amplitude but of relatively longer duration. The important factor in determining visibility, consequently, is the quantity of light as determined by integrating the light intensity over time. p 7

It is the principal object of the present invention to increase the penetrating capabilities of warning lights by increasing the time duration of the flashing signal rather than its amplitude. Through this particular design of the present invention, the operating life of the equipment is considerably increased since a higher amplitude signal places stress upon the transmitting lamp and the equipment used to operate the lamp. In addition, considerable saving is incurred through the use of the present invention, since the equipment can be less complex and therefore less costly. When resorting to large amplitude pulsed light signals, for example, special equipment is generally required to accommodate the handling of the large voltage or signal potentials that may be involved. Through the use of the present invention, therefore, such disadvantages are avoided.

SUMMARY OF THE INVENTION An automatic control arrangement for varying the characteristics of a flashing warning light, at sea, as a function of the prevailing fog conditions. Under normal conditions a flashing light is transmitted from a warning, installation for the purpose of guiding mariners at sea to avoid hazardous conditions. A light signal receiver in the form of photoelectric cells is also located at the warning installation and receives a portion of the transmitted light in the form of a backscattered signal. When fog sets in, the amount of backscattered light increases, and 'thus the amplitude of the received signal from the photoelectric cells increases correspondingly. When this received signal exceeds a predetermined threshold level, an amplifier operates a relay which, in turn, switches an inductance component into the light transmitting circuitry. The transmitting lamp may be in the form of a spark discharge lamp and fed from a discharge capacitor which is, in turn, charged from a DC power supply. The magnitude of the discharged light pulse may be increased through the use of an additional capacitor in parallel with the capacitor operating under normal conditions. The additional or auxiliary capacitor can, in thiszmanner, provide the additionalenergy necessary to increase the amplitude of the flashing pulse. When the relay is switched under sufficiently heavy fog conditions, and the inductance is switched into the circuit, the duration or time interval of the transmitted light pulse is increased rather than its amplitude.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an isometric elevational view of the warning light installation and shows the relationship of transmitter in receiver so that they do not interfere with each other, in accordance with the present invention; and

FIG. 2 is a functional electrical schematic diagram showing the interconnection of the transmitter and receiver, whereby the time duration of the transmitted light pulse is increased under fog conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, the warning signal arrangement, in accordance with the present invention, is mounted upon a tower 10 off the seashore. The mounting base 10 could also be in the form of a floating drydock or other marine installation. Furthermore, the arrangement in accordance with the present invention is quite adapted for use on land to warn, for exam ple, aircraft of hazardous obstructions at a predetermined altitude. It is thus seen, that the invention is not restricted to marine applications.

The signal transmitter 11 is enclosed within, for example, a circular housing in the form of a Fresnel lens. By surrounding the entire transmitter 11, the housing 12 permits omnidirectional transmission from the transmitter 11. The receiver 13 is mounted directly above the transmitter 11 on the same mounting 10. The receiver 13 is also enclosed within a housing 14 constructed in the form of a Fresnel lens. The Fresnel lens 12 assures that the transmission of the optical signal from the transmitter 11 is directed along a substantial omnidirectional horizontal plane. The Fresnel lens 14, on the other hand, allows the receiving of signals directed along a substantially horizontal plane. The separating member 15 is interposed between the transmitting housing '12 and the receiver housing 14, in order to prevent any signal from the transmitter to impinge directly upon the receiver. Thus, it is desired that the receiver 13 receive a portion of the optical signal 16 which results from backscatter conditions only. It is not desired that the transmitted signal 17 be routed so that any portion of it directly impinges upon the receiver. If such a direct signal were to be applied to the receiver, the latter would become overloaded and would not be able to distinguish between clear weather and fog conditions. By confining the received signal 16 to the portion which is backscattered from the fog within the air only, an indication of the prevailing fog conditions may be realized. Accordingly, the separating member 15 must extend sufficiently along the horizontal plane so as to assure physical separation between the transmitted and received energy. A sloping roof 18 is provided above the receiver so as to protect the latter from penetration of rain and, for example, birds. It is not essential that the receiver 13 be mounted above the transmitter 11. It is quite feasible that the reverse construction be applied in which the transmitteris mounted above the receiver. The net results of the arrangement are the same in either situation.

As shown in FIG. 2, the transmitter 11 includes a lamp 20 for the emissionof an optical signal. The lamp 20 may be in the form of a spark discharge lamp which is pulsed at regular intervals. By pulsing the lamp in this manner, a human observer at a distance from the lamp may detect a flashing signal. The discharge of energy across the electrodes of the lamp 2t] is accomplished by a discharge Capacitor '21. The latter is charged from a power supply 22 which may be'in the form of 'a battery. A power inverter 23 interposed between the battery 22 and the discharge capacitor 21 converts the voltage energy of the batteries suitable for charging the capacitor. A variable inductor 24 connected between one electrode of the lamp 20 and one plate of the capacitor 21 serves to modify the discharge pulse of the capacitor 21 so that the operating life of the lamp 20 is substantially increased. The discharge capacitor 21 is, itself, connected directly across the voltage supply 22 by way of the power inverter 23. One plate or electrode of the capacitor 21 is directly connected to one electrode of the lamp 20. The other plate or electrode of the capacitor leads to the other electrode of the lamp 20 by way of the variable inductor 24. The variable inductor may be set as desired, to modify the pulse from the discharge capacitor 21, so' as to provide an optical signal of the desired intensity and, at the same time, realize a predetermined operating life of the lamp 20.

Under fog conditions, the distance from which the flashing signal emitted by the lamp 20 may be seen, diminishes,

assuming all other factors remaining equal. Therefore, to

maintain the warning light visible at the same distance even when fog conditions set in, it is essential to either increase the amplitude of the transmitted signal, the time duration of the signal, or both. Thus, the optical signal detected by the human eye at a given distance from the lamp 20, depends upon the integral of the amplitude of the signal as a function of time.

The modification of the emitted signal from the lamp 20 is accomplished through an LC network switched in parallel with the capacitor 21, on the predetermined fog conditions. This LC network includes a further or auxiliary discharge capacitor 26 and an inductor 25. The discharge capacitor 26 is charged from an auxiliary power supply 27. The auxiliary discharge capacitor 26 is connected directly across the output terminals of the auxiliary power supply 27. One electrode of the capacitor is also connected directly to one plate or electrode of the capacitor 21. The other plate or electrode of the capacitor 26 is connected directly to one terminal of the inductor and to the output terminal of the auxiliary power supply 27. The other terminal of the inductor 25 leads to a switching contact 28 of a relay 30.

The electromagnetic relay 30 has an electromagnetic coil 32 which, when energized through an electrical signal, actuates the removable switching contact 34. -When the movable contact 34 is actuated through the electromagnetic field generated by the coil 32, the contact 34 is in electrical contact with the fixed terminal or contact 28. As a result of such actuation of the relay 30, therefore, the LC network consisting of inductor 25 and capacitor 26 is connected directly across the capacitor 21.

In particular, the terminal 21a of the capacitor 21 is directed to the terminal 26a of the capacitor 26. The terminal 25a of the inductor 25 is connected to the fixed contact 28 of the relay 30. The movable contact 34 of the relay is directly connected to the plate or electrode 21b of the capacitor 21. Accordingly, when the relay is actuated and closure of the movable contact 34 is obtained, the series combination of the capacitor 26 and inductor 25-is applied directly across the capacitor 21. At the same time, the auxiliary power supply is connected directly across the capacitor 26.

The capacitor 26 when connected across the capacitor 21 by way of the inductor 25, may be considered to aid in the formation or increasing of .the amplitude of the transmitted optical signal from thelamp 20. The inductor 25, on the other hand, may be considered to increase the time duration of the signal. The inductor 25 is an essential element and component of the present invention because it serves to increase the fog penetrating characteristics of the optical signal without materially affecting the operating life of the lamp. Thus, as noted supra the optical signal detected by the human eye depends upon the time integral of the amplitude of the signal.

Therefore, the same net effects maybe realized through either increase-in amplitude or an increase in the time duration of the signal. Since an'increase in the amplitude'of the signal produces various disadvantages from the viewpoints of complexity of the equipment and its operating life, the increase in the time duration of the signal is the preferred method. As a result,-the present invention provides for the inductor 25 which materially increases the time duration of the signal transmitted when fog conditions prevail, and therefore makes it unnecessary to materially increase the amplitude of the signal.

The LC network consisting of inductor 25 and capacitor 26 is switched into the circuit by the relay 30 when the prevailing fog has attained a predetermined level. The detection of the fog conditions is established by the receiver 13 having a photosensitive element 40. The photosensitive element 40 is mounted within the Fresnel lens enclosure 14 so that it may function as an omnidirectional receiver. The photosensitive element 40 converts the portion of the signal 16 received as backscattered energy from the fog within the atmosphere, into an electrical signal. This signal is then applied across a resistor 42. A battery or voltage supply 43 maintains the photoelectric circuit energized so that any light energy 16 impinging upon the photosensitive component of the circuit appears as a substantial signal across the resistor 42.

The voltage supply or battery 43 is connected in series with the resistor 42, and the series combination is, in turn, connected directly across the photosensitive receiver 40. A signal amplifier 45 is connected across or in parallel with the resistor 42. The output of the amplifier 45 is applied to the boil 32 of the electromagnetic relay 30.

The signal appearing across the resistor 42 as a result of the energy impinging upon the photosensitive element 40, is ordinarily not sufficient to maintain an electromagnetic relay 30 energized. As a result, an amplifier 45 is interposed between the resistor 42 and the boil 32 of the electromagnetic relay 30. The signal amplifier 45 serves to amplify the signal appearing across the resistor 42 so that sufficient energy and voltage amplitude is available for maintaining the relay 30 actuated in a reliable manner. The amplifier 45 is of standard construction and well known in the art to be commercially available.

In operation, the received energy 16 is converted into an electrical signal with voltage appearing across the resistor 42. This voltage signal is amplified by the amplifier 45. When this signal has attained a predetermined level, signifying that the fog is of a predetermined magnitude, the amplifier output is of the amplitude sufficient to actuate the relay 30. Accordingly, the LC network of inductor 25 and capacitor 26 will be switched in into the circuit and become active when the fog has attained a predetermined magnitude as represented by the signal output of the amplifier 45.

It is to be noted that the arrangement, in accordance with the present invention, is not confined to one single switching circuit whereby a switching operation takes place at only one predetennined level of the fog magnitude. It is quite feasible, for example, to include a bank of such switching circuits having a plurality of similar such relays 30 which are switched in sequence at progressive amplitudes of the signal output of the amplifier 45. With such a design, the time duration of the flashing signal may be progressively increased as the fog density increases.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of electronic warning signal arrangement differing from the type described above.

While the invention has been illustrated and described as embodied in electronic warning signal arrangement, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various application without omitting features,that, from the standpoint of prior I signal under fog conditions, comprising, in combination, a

signal transmitter transmitting an optical signal at'periodic intervals through an atmospheric environment laden with fog;

' signal varying means connected tosai d transmitter for varying the time duration of each of said optical signals transmitted through the fog; signal receiver means mounted in the region of said signal transmitter outside of the path of said optical signals transmitted by said transmitter and adapted to receive a portion of the optical signals back-scattered by the fog in the atmosphere for generating electrical control signals proportional to the intensity of said optical signals received by said signal receiver means, the intensity variations of said electrical control signals thus being proportional to the variations of the intensity of the fog in the atmosphere; and actuating means controlled by said electrical control signals for'actuating said signal varying means so as to increase the time duration of said optical signals transmitted by said signal transmitter whenthe intensity of said electrical control signals increases and so as to decrease the length of said optical signals transmitted by said signal transmitter when the intensity of said electrical control signal decreases, whereby the time duration of the transmitted signals is increased with increasing fog density and decreased with decreasing fog density, respectively, so that the visibility of said transmitted optical signals at a predetermined distance from said transmitter remains substantially inde conditions.

2. A warning signal arrangement as defined in claim 1, wherein said signal transmitter includes a spark discharge lamp, and a discharge capacitor connected to discharge through said lamp, and wherein said signal varying means includes an inductor that is connected across said discharge capacitor when said actuating means actuates said signal varying means to increase the time duration of said optical signals and that is not connected across said discharge capacitor when said actuating means actuates said signal varying means to decrease the length of said optical signals.

3. A warning signal arrangement as defined in claim 2, wherein said signal varying means further includes an auxiliary discharge capacitor connected in series with said inductor, whereby said inductor and auxiliary discharge capacitor are connected in series across said discharge capacitor when said actuating means actuates said signal varying means to increase the time duration of said optical signals.

4. A warning signal arrangement as defined in claim 3, wherein said signal varying means further includes an auxiliary power supply connected to charge'said auxiliary discharge capacitor.

5. A warning signal arrangement as defined in claim 2, wherein said actuating means includes relay means operated by said electrical control signals for connecting said inductor in parallel with said discharge capacitor to increase the time duration of said optical signals and to remove said inductor from the circuit of said discharge capacitor to decrease the time duration of said optical signals.

6. A warning signal arrangement as defined in claim 5, including amplifier means connected to said relay means for amplifying said electrical control signals before application of the latter to said relay means.

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1. A warning signal arrangement transmitting a warning signal under fog conditions, comprising, in combination, a signal transmitter transmitting an optical signal at periodic intervals through an atmospheric environment laden with fog; signal varying means connected to said transmitter for varying the time duration of each of said optical signals transmitted through the fog; signal receiver means mounted in the region of said signal transmitter outside of the path of said optical signals transmitted by said transmitter and adapted to receive a portion of the optical signals back-scattered by the fog in the atmosphere for generating electrical control signals proportional to the intensity of said optical signals received by said signal receiver means, the intensity variations of said electrical control signals thus being proportional to the variations of the intensity of the fog in the atmosphere; and actuating means controlled by said electrical control signals for actuating said signal varying means so as to increase the time duration of said optical signals transmitted by said signal transmitter when the intensity of said electrical control signals increases and so as to decrease the length of said optical signals transmitted by said signal transmitter when the intensity of said electrical control signal decreases, whereby the time duration of the transmitted signals is increased with increasing Fog density and decreased with decreasing fog density, respectively, so that the visibility of said transmitted optical signals at a predetermined distance from said transmitter remains substantially independent of varying fog conditions.
 2. A warning signal arrangement as defined in claim 1, wherein said signal transmitter includes a spark discharge lamp, and a discharge capacitor connected to discharge through said lamp, and wherein said signal varying means includes an inductor that is connected across said discharge capacitor when said actuating means actuates said signal varying means to increase the time duration of said optical signals and that is not connected across said discharge capacitor when said actuating means actuates said signal varying means to decrease the length of said optical signals.
 3. A warning signal arrangement as defined in claim 2, wherein said signal varying means further includes an auxiliary discharge capacitor connected in series with said inductor, whereby said inductor and auxiliary discharge capacitor are connected in series across said discharge capacitor when said actuating means actuates said signal varying means to increase the time duration of said optical signals.
 4. A warning signal arrangement as defined in claim 3, wherein said signal varying means further includes an auxiliary power supply connected to charge said auxiliary discharge capacitor.
 5. A warning signal arrangement as defined in claim 2, wherein said actuating means includes relay means operated by said electrical control signals for connecting said inductor in parallel with said discharge capacitor to increase the time duration of said optical signals and to remove said inductor from the circuit of said discharge capacitor to decrease the time duration of said optical signals.
 6. A warning signal arrangement as defined in claim 5, including amplifier means connected to said relay means for amplifying said electrical control signals before application of the latter to said relay means. 